Can't run Prime95 more than 4 hours

Hello, I'd very much like some help resolving stability issues I'm having.

Prime95's In-place large FFTs torture test always fails on my PC, lasting between 30 minutes and 4 hours. The Small FFTs test, on the other hand, has run fine for at least 10 hours before I had to shut it down. And Memtest recorded no errors after 24 hours. As a result, my guess is that it's the CPU (which is why I'm posting here) but for all I know I could be totally wrong. I just need help trying to determine exactly what the problem is, and if I can fix it without buying a new CPU.

I'll provide any info that's required to help me, but without knowing what that will be, here are the basics:
- OS: Windows XP
- CPU: AMD Athlon 64 3500+ S939 Newcastle
- Motherboard: DFI Lanparty NF4 Ultra-D
- Memory: OCZ Dual Channel Optimized 2x512MB DDR PC3200 (I think this is from OCZ's Gold product line.)
- Speedfan reports that CPU temp while running Prime95 ranged from 55C to 60C. Room temperature went as high as 25-30C.
- I know nothing about overclocking, so I would imagine my system isn't overclocked, but I did set my BIOS to "Load Optimized Defaults". There is no other option, though.
- The Prime95 failures happened before and after a recent system reformat.

Please let me know what other info I can provide or tests I can run in order to get to the bottom of my problem.

7 answers Last reply
More about prime95 hours
  1. It's probably a memory thing.
    Try to lower your timing a bit then test again.

    I think memtest doesnt torture your system enough.

    Also get some air circulating around your HSF and memory.
  2. Should I start by just increasing all 4 numbers by 1, or modify one at a time? In the latter case, which one should I try increasing first?
  3. Maybe you should set your bios to Load default or fail safe setting instead of Load optimized defaults.... That might improve your stability.
  4. Unfortunately, my BIOS doesn't have anything besides "Load Optimized Defaults". It doesn't really matter in this case, though, because the BIOS sets 3 of the 4 numbers to Auto. The 4th (the one that's always the highest) is set to 6. The memory timings always quickly appear on screen at boot, and if I recall, they're currently 2-3-6-2. (Shouldn't that have been written 2-3-2-6?) Anyway, I'll confirm it when I get home. Would it help at all if I gave you all the memory settings from my BIOS?
  5. 60C is top end for that chip and it would be better to not go over 50C.
    As the memory past the test,and prime is a CPU stress test,it looks like your overheating.

    It should be fine however becuase you will never use 100% CPU for that long a time while game playing.

    You may want to remove the fan grill on the case for full airflow as even with a stock cooler the temps drop more than a CPU cooler upgrade and it's free to do.
  6. I just tried increasing the 4 memory timing numbers by 1 each, and afterwards my PC was unable to even reach the BIOS. Or maybe it did, but my screen refused to turn on so it wouldn't have mattered. I ended up having to reset the CMOS. Suffice it to say, I don't think I'll be playing with those numbers again unless I get specific instructions.

    At the very least, I know have default BIOS settings loaded, which may or may not be different from the optimized defaults. I'll run Prime95 overnight and see what happens. I was able to run the Small FFTs for over 12 hours today, with the CPU temp reaching 55-60C. Really, it's only the In-place large FFTs test that's causing problems, whatever that means.

    As for temp, I agree that that seems rather higher. The bad news is that these temps were recorded with the side of the case off. I don't see what I could do besides optimizing my wire placement inside my case. I'll see what I can do.

    Thanks for the help you've all provided!
  7. Small FFTs error is a CPU problem.
    Large FFTs error is a memory problem.

    Maybe you can get a photo of your bios setting so we can tell you what to change.

    Let me tell you it's a bit strange to have this kind of error with bios defaults.
    It could be the mobo fals reading the memory eprom and pushing the memory chips too far or they are simply not good enough.

    It could also be some overheating issue but I think it's a bit unlikely.

    Open your case and put a fast fan to blow air onto the memory and then test with large FFTs. Maybe the memory gets overheated.
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